5.1.2 says "If a locator-type element has anything other than an
extended-type element for a parent, the locator-type element has no
XLink-specified meaning." 5.1.3 makes a similar statement for arc-type
elements. I expected 5.1.1 to contain a similar statement for
resource-type elements, but I couldn't find it.
5.1 says "Subelements of the locator, arc, or resource type that are not
direct children of an extended-type element have no XLink-specified
relationship to the parent link." The following subsections make a
rather stronger statement, namely "that they have no defined meaning".
I would suggest 5.1 say the same.
I couldn't understand why the sample DTD in Appendix B makes the label
attribute required for the locator-type element but not required for the
resource-type element.
James